Various industries are increasingly turning to large-scale equipment to meet operational demands. As industry develops large-scale equipment, it seeks large-scale components, such as seals and o-rings. Often, the large-scale equipment is located in remote harsh environments, increasing demand for durable and hardy seals. For example, as the oil and gas industry seeks to drill in deeper water, the scale of the equipment used is increasing and, as a result, the demand for more durable, large-scale products that can survive harsh environments increases.
PTFE filled polymers are highly desirable for a variety of applications such as large diameter seal rings, back-up rings, or other seal devices (collectively referred to as seal rings herein). These large diameter seal rings are often used, for example, by the oil and gas industry. As used herein, the phrase “large diameter” will be used to describe diameters of at least 600 mm. Such large diameter seal rings cannot be easily made by conventional molding techniques used for smaller rings.
One method of forming these types of large diameter rings is described in U.S. Pat. App. No. 2010/0116422 by Vaideeswaran et al., for “Method of Forming Large Diameter Thermoplastic Seal,” which is assigned to the assignee of the present application and which is hereby incorporated by reference. According to the method described by Vaideeswaran, large diameter seal rings are formed using extruded thermoplastic rods, which are bent into a circular shape and then welded together at the ends to form a seal ring.
Unfortunately, PTFE filled materials, while highly desirable for their wear characteristics and low friction, are often difficult to use with typical heat welding processes. Specifically, the welded portion of a PTFE polymer will often show a reduced elongation to break as compared to the unfilled polymer. This makes such PTFE filled materials less suitable for applications such as large diameter seal rings, back-up rings, or other seal devices, where an elongation to break of at least 3% is desirable.
As such, a new method of forming a large-diameter seal using polymers filled with PTFE or other fillers would be desirable.